Scalzi has taken a public stand recently saying he won’t speak at or attend conferences unless they have a published, enforced anti-harassment policy. So this might have something to do with that. He’s also tweeted quite a bit recently about people disgruntled about his Hugo win, so that’s another option.
But I’m guessing this is a bigger thing – he’s a public person, and I imagine he gets quite a bit of crap from random jerks because of that. So it might not be related to either of those things in particular, which would explain why he posted it without context.
